Wiper roll inking device for printing machines using fatty inks



Nov. 8, 1966 L. J. CHAMBON WIPER ROLL INKING DEVICE FOR PRINTINGMACHINES USING FATTY INKS 5 Sheets-Sheet 1 Filed Jan. 5, 1966 Nov. 8,1966 L. J. CHAMBON 3,233,712

WIPER ROLL INKING DEVICE FOR PRINTING MACHINES USING FATTY INKS FiledJan. 5, 1966 5 Sheets-Sheet 2 United States Patent 3,283,712 WIPER ROLLINKING DEVICE FOR PRINTING MACHINES USING FATTY INKS Louis Jean Chambon,Paris, France, assignor to Societe dEtudes de Machines Speciales, Paris,France Filed Jan. 3, 1966, Ser. No. 518,045 Claims priority, applicationFrance, Sept. 21, 1962, 910,165, Patent 1,341,700; Dec. 10, 1962,918,075, Patent 1,341,700

1 Claim. (Cl. 101-350) This patent application is a continuation-in-partof my prior patent application Ser. No. 309,531 filed on September 17,1963, now abandoned.

The present invention relates to a device for distributing a thinregular film of high-viscosity liquid on the surface of a cylinder orroller lined with or consisting of flexible material, this device beingapplicable notably to the inking of fatty-ink printing machines such asoffset machines.

These printing machines comprise a roller lined with flexible material,called inking roller, receiving ink from an inking device and adapted todeposit said ink onto an etched portion of the printing cylinder orroller. The inked portions of the etching take a certain amount of inkfrom the ink film carried by the outer peripheral surface of the inkingroller but no ink is taken by the nonetched or plain portions of theprinting cylinder. Under these conditions, when the inking of saidetched portions is completed the inking roller has inked residualsurface portions called transfers.

Inking devices are already known wherein the residual ink transfersformed on the surface of the inking roller are blended into a mass ofink contained in the space overlying the line of mutual contact of saidinking roller and ink feed roller, the thickness of the ink filmdeposited on the surface of the inking roller being adjusted by varyingthe pressure exerted on this roller by the ink feed roller.

However, these devices are always equipped with equalizing rollerstangent to the inking roller in the surface area of the inking rollerwhich extends from the aforesaid line of mutual contact of said inkingroller with the ink feed roller to the line of contact of said inkingroller with the etched or printing cylinder.

It is one of the essential objects of the present invention to providean improved device for inking the inking roller lined with flexiblematerial in a fatty-ink printing machine, this device beingcharacterized primarily by an extremely simplified structure.

It is another object of this invention to provide a device for inkingthe inking roller lined with flexible material in a fatty-ink printingmachine, wherein the thickness of the ink film deposited on theperipheral surface of the inking roller can be controlled in aparticularly simple manner without requiring the use of an equalizingroller.

Furthermore, this invention also contemplates the provision of a devicefor inking the inking roller lined with flexible material in a printingmachine utilizing fatty ink, whereby a strictly constant ink-filmthickness is obtained on the inking cylinder, throughout the lengththereof.

This invention is based on the discovery, resulting from experimentalworks, that if for a given ratio of the velocities of rotation of theinking roller and ink feed roller, respectively, the pressure betweenthe inking roller lined with flexible material and the ink feed rollerof rigid material exceeds a certain critical threshold corresponding toa given compression of the lining of said inking roller, the thicknessof the ink film deposited on the outer peripheral surface of said inkingroller lined with flexible material will remain practically unchangedand attain a value corresponding substantially to a limit thickness.This is due to the fact that the flexible material lining the peripheralsurface of the inking roller yields when the pressure value overstepsthis threshold. Thus, if the pressure produced between the flexiblesurfaced inking roller and the rigid-surfaced ink feed roller is kept ata value in excess to said critical threshold,'the thickness of theresulting ink film spread throughout the length of the ink feed rollerwill be strictly constant and inferior or equal to the limit thicknesscorresponding to the threshold of critical pressure. An ink-filmthickness inferior to said limit thickness may be obtained by adjustingaccordingly the velocity of rotation of the ink feed roller having thecomplementary function of a wiper roller. In fact, the higher thevelocity of rotation of this ink feed roller, the thinner the ink filmcarried by the peripheral flexible surface of the inking roller.

The inking device according to this invention is also characterized by avery important featureover hitherto known devices. In fact, since theinking roller lined with flexible material and the rigid-surfaced inkfeed roller have a'certain length and the contact pressure is obtainedby altering the relative positions of the ends of the shafts of theserollers, the local pressure at any selected point of the contactgeneratrix is not strictly constant throughout the length of theserollers as a consequence of their flexibility. It is thus clear that ifit is desired to adjust the thickness of the ink film by simplyadjusting the contact pressure between the two rollers, local pressurevalues that are not constant along the contact generatrix are obtained,thus causing detrimental inequalities in the thickness of the ink filmon the surface of the inking roller.

On the other hand, in the inking device according to the presentinvention if the contact pressure between the two rollers is adjusted ata pressure value such that the local pressure at any point selectedalong the contact generatrix be always superior to the above-definedcritical pressure threshold, the ink film spread on the peripheral.

surface of the inking roller has a reliably constant thicknessthroughout the length of this roller, this thickness being equal to orlower than the limit thickness. The actual value of this thickness issubordinate to the velocity of rotation of the inking roller which thenacts as a wiper roller.

A typical form of embodiment of the present invention will now bedescribed by way of example with reference to the attached drawings inwhich:

FIGURE 1 is a diagrammatic elevational view showing an inking deviceconstructed according to the teachings of this invention.

FIGURE 2 is a developed diagram showing the surface of the inking rollerof flexible material to illustrate the various operations carried out onthis roller.

FIGURE 3 is a fragmentary view showing on a larger scale the contactzone between the inking and ink-feed rollers.

FIGURE 4 is a diagram illustrating the variation in the thickness of theink fihn between the two rollers for a zero velocity of rotation of theink feed roller, as a function of the sag resulting from the compressionof the flexible material lining the inking roller.

FIGURE 5 is a diagram showing the equipment utilized for theexperimental works having led to the present invention.

FIGURES 6, 7 and 8 are other diagrams illustrating the results of thetests made by utilizing the equipment shown in FIGURE 5.

In the following description reference will be made to an offsetprinting machine operating with fatty ink, but it will readily occur toanybody conversant with the art that this invention is applicable aswell to any machine or device involving the distribution of a thin,regular film of high-viscosity liquid to the outer surface of a cylinderor roller lined with flexible material.

In FIGURE 1 there is illustrated an etched roller 1 of a printingmachine which receives ink from an inking roller 2 lined with flexiblematerial (plastic or rubber). An ink feed roller 3 (constituting in factas a rule an ink distributor and wiper roller) is kept in contact withthe inking roller 2 along a contact generatrix designated by thereference numeral 4.

Overlying this contact generatrix 4 is a mass or fountain of ink 5filling the lower portion of the space bounded by the peripheralsurfaces of these two rollers.

The etched cylinder 1 and inking roller 2 are rotatably mounted on afixed frame structure 7, and the ink feed roller 3 is rotatably mountedon a support 8 fulcrumed on a shaft 9. A hydraulic cylinder 10 permitsof adjusting at will the contact pressure between rollers 2 and 3.

Rollers 1, 2 and 3 are rotatably driven in the direction shown by thecorresponding arrows by means of motors 11 and 19. The motor 11 drivesthe etched cylinder 1 and inking roller 2 by means of a train of gears15, and motor 19-drives the ink feed roller 3 through the intermediaryof another train of gears shown only diagrammatically at 16.

The inking roller 2 and ink feed roller 3 revolve in a clockwisedirection; thus, their adjacent or contact surfaces move in oppositedirections and under these conditions the ink feed roller 3 also acts asa wiper-with respect to the inking roller 2.

The reserve or fountain of ink 5 is retained by a doctor 12 engagingwith its operative end the outer periphery of inking roller 3 above thecontact generatrix 4.

Referring now to FIGURE 2 it will be seen that the relief or projectingportions 1a of etched cylinder 1 take a certain amount of ink from theink film 6 coating the peripheral surface of inking roller 2, after thecontact generatrix 4, and that no ink is taken therefrom by the hollowportions 1]) of said printing cylinder. As a result, ink-free zones 6aare formed in the ink film 6 which correspond to the inked portions 1aof etched cylinder 1, and other zones 6b are also formed wherein the inkthickness is unchanged and constitute what is commonly referred to astransfers. These ink tranfers 6b appearing on the outer surface ofinking roller 2 after the transfer of ink to the etched cylinder 1a arefed to the mass of ink 5 and left therein. Thus, downstream of thecontact generatrix 4 between the ink feed roller 3 and the inking roller2, an ink film 6, of which the thickness is adjustable in a strictlyconstant and uniform manner by means of the present invention, isdeposited on the inking roller 2.

The ink film thickness is adjusted by modifying two parameters, namelyon the one hand the pressure existing in the nip 4 between the rollers 2and 3, and on the other hand the relative rotational speed of these tworollers. In fact, it was observed that in offset machines having aninking roller 2 lined with flexible material it is not possible toreduce the thickness of the ink film 6 carried by the surface of thisinking roller 2 beyond a certain limit thickness even if the pressurebetween the ink feed roller 3 and inking roller 2 were increasedconsiderably. The results of the theoretical study and also of thepractical tests having confirmed the theoretical anticipations.

Referring now to FIGURE 3 it will be seen that the nondeformableink-feed and wiper steel roller 3 having a radius R and the deformableinking roller 2 having a radius R and a rubber-lined surface revolve inthe same direction; in other words, their adjacent surfaces move inopposite direction in the contact zone, respectively at speeds v (inkfeed roller 3) and v, (inking roller 2).

Assuming that these rollers 2 and 3 are pressed against each other, inthe absence of the reserve of ink 5, it will be seen that the rubberlining of the inking roller 2 is squeezed to an extent or sag ddepending on the pressure produced between the two rollers. If the ink 5is fed into the pocket formed above the nip of these rollers an ink filmhaving a thickness 11 is carried along between the two rollers 2 and 3,thus applying to the inking roller 2 a compression d+h. The pressure pbetween these two rollers varies between the points A and B representingthe limits of the compression zone of the inking roller 2, as shown inFIGURE 3.

A theoretical calculus, assuming that the ink feed roller 3 isstationary (1 :0) and that a throttled flow of ink takes place betweenthese two rollers, leads to the following relationship:

wherein K is a constant and l1, the thickness of the ink film betweenthe two rollers when speed v =0.

If the curve h =f(d) is traced, the diagram of FIG- URE 4 will beobtained. In this figure, the squeezing d of the inking roller, beforeintroducing any ink, is plotted in abscissa against the thickness h ofthe ink film between the two roller, in ordinate.

It will be seen that curve h =f(d) has an oblique asymptote if d hasnegative values corresponding to the existence of a gap between therollers 2 and 3.

If d has positive values corresponding to the application of pressurebetween rollers 2 and 3, this curve will admit to infinity the axis ofthe values of d as an asymptote.

It will be seen that beyond a given value of d, that is, when thepressure between rollers 2 and 3 exceeds a certain threshold, aconsiderable variation Ad of d involves a very small variation Alto of hOn the other hand, considering the thickness e of the ink film at theouter periphery of inking roller 2 beneath point B, the followingrelationship can be easily determined according to the law of themechanics of fluids. From this relationship it is clear that thethickness 2 of the ink film may be varied by modifying the ration v /vAn experimental equipment designed for controlling the theoreticalresults obtained by calculation will now be described, the results ofthe tests carried out with various types of ink being given thereafter.

This experimental equipment is shown in diagrammatic form in FIGURE 5,wherein the component elements corresponding to those of FIGURE 1 aredesignated by the same reference numerals. The inking and ink-feedrollers 2 and 3 revolve in the same direction at speeds v and vrespectively. The inking roller 2 is lined with rubber and adapted tosupply ink to the plate; in practice, its speed is subordinate to theplate speed and therefore to the machine speed. The ink feed roller 3 ischromiumplated to withstand the frictional contact of doctor 12 and actsaccessorily as a wiper; its speed v will be adjusted to vary the ratio v/v and therefore the thickness e of the ink film deposited on the outerperiphery of inking roller 2. The purpose of the measurements madeduring these tests was to study the variations in the thickness of theink film left on the inking roller 2 after the wiping thereof by roller3. To this end, for a given ratio and ink grade, the two rollers 2 and 3are moved towards each other (by means of the hydraulic cylinder oractuator 10 of FIG- URE 1) in order to obtain firstly a negativepressure therebetween when these rollers are somewhat spaced from eachother, then a certain positive pressure when the inking roller 2 issqueezed by the ink feed roller 3.

The position of ink feed roller 3 is checked by means of two comparators17 disposed at either end of roller 3. The compression d of the inkingroller 2 is positive when the distance between centers of these rollersis smaller than the theoretical or actual value R +R and negative in theother alternative.

The thickness of the ink film carriedby the surface of the inking roller2 after the wiping action produced by the ink feed roller 3 isdetermined by means of a cup 18 held in contact with the surface of theinking roller 2 during a number of revolutions N of this roller, wherebyits leading edge having alength a will scrape off completely any inkleft on the surface of inking roller 2. Thus, all the ink carried by asurface corresponding to a 2R N is collected. Weighing this ink willgive, by means of a very simplecalculation, the average thickness e ofthe ink film during N revolutions.

' The results of these measurements concerning two types of ink aregiven hereinafter.

F irst test This test was carried out under the following conditions:

Velocity of rotation of inking roller 2 v =2O m./mr1. Velocity ofrotation of ink feed roller 3 v and v =m./mn. Hardness of rubber liningof roller 2 u Shore No. 45 Radius of inking roller 2 R =65 mm. Radiousof ink feed roller 3 R =65 mm. Ink viscosity 2poises.

The results are summarized in Tabe I hereinafter and also in the diagramof FIGURE 6 of the attached drawing, wherein the squeezing d in mm. isplotted in abscissa against the thickness e of the ink film in ordinate.In this diagram, curve A corresponds to a ratio v /v =0 and curve B to aratio v /v =.5.

c e (microns) (microns) Second test This test was carried out under thefollowing conditions:

Velocity of rotation of inking roller v =30 m./mn. 2 v =variableVelocity of rotation of ink feed roller from 0 to 21 m./mn. Hardness ofrubber lining of roller 2 Shore No. 45. Radius of inking roller 2 R =65mm. Radius of ink feed roller 3 R =65 mm. Ink viscosity 2poises.

The results are summarized. in Table II hereinafter and also in thediagram of FIGURE 7 of the attached drawing, wherein the curves C, D, E,F and G correspond to the following values of ratio v /v 0; .15; .3; .5;.7.

TABLE II d velvt=0 v../vt=0. 15 71e/ t=0. 3 Ila/=0. 5 .ve/vt=0. 7 mm.

c e e s e (a) (F) (u) (a) (u) in ordinate.

The curve H is a straight line corresponding to the theoretical law ah19) e- 2 1 m determined by calculation, and curve I obtained by interconnecting the points found experimentally is determnied from the curvesof FIGURE 7.

Therefore, to obtain on the peripheral surface of inking roller 2 an inkfilm 6 having a strictly constant thickness throughout the length ofthis roller, the following procedure must be adhered to: After havingpoured a reserve or fountain of ink 5 above the nip of rollers 2 and 3in muaual contact, the cylinder or actuator 10 is actuated in order toproduce in said nip 4, between the rollers 2 and 3, a pressure higherthan the critical pressure threshold beyond which any additionalincrement of said pressure does not produce any appreciable variation inthe thickness of the ink film. To this pressure threshold corresponds agiven value d of the'rubber squeezing which may be selected, forexample, from the set of curves of FIGURE 6, to be 0.8 mm. The pressureexerted by the cylinder 10 should be sufficient to cause the localpressure exerted at any point along the contact generat rix 4 to exceedsaid critical pressure threshold, so that, irrespective of thedeformation to which the rollers 2 and 3 are subjected by this pressure,the thickness e of the ink film 6 remains constant throughout the lengthof the inking roller 2. This thickness, which is for example 4.89u (seeTable I, and FIGURE 6) for a squeezing sag d =0.8 mm. and a speed ratiov /v,=0, may be adjusted to the desired value lower than 4.89;]. byadjusting the velocity of rotation of the wiper roller 3 after the curveI of FIGURE 8. The higher the velocity of rotation of ink feed roller 3,the thinner the ink film 6.

Thus, the experiment confirms the fact that the varia. tion in thethickness e of the ink film is immaterial in sprite of considerabledifferences in the squeezing value d, when d exceeds a predeterminedcritical value.

The mechanical defects such as eccentricity, fiexion, etc. likely toalter d (value of initial squeezing or pressure chosen initially) may beseveral tenths of .a millimeter without inasmuch interfering with theregularity of the ink layer.

In fact, it may be said that when a roller or cylinder is out of true byabout .05 mm. this value is considerable.

On the other hand, a one-meter long steel roller having a diameter of100 mm. and to which a load corresponding to one millimeter of squeezingis applied will yield only by .05 mm.

The variation in the flexible roller squeezing d as a consequence ofmechanical defects would therefore total only .1 mm.

Now if we refer to the diagram of FIGURE 7, it Will be seen on curve Bcorresponding for example to a ratio v /v =.3 for a variation Ad=.l mm.,the variation in the ink film is of the order of which is negligible.

FIGURE 1 shows that the doctor 12 substantially prevents any ink filmfrom continuing to adhere to the outer surface of roller 3 after thisdoctor 12. However, if the ink film is not removed completely as shownin FIGURE 1 another doctor 13 may be provided which has its operat-iveend disposed tangent to the ink feed roller 3 in the zone where thegeneratrices of this ink feed roller 3 move downwards, that is, on theright-hand side of this roller as seen in FIGURE 1. This additionaldoctor 13 makes a completely ink-free surface :after it, and may alsoserve a complementary function when it is desired to remove the reserveof ink 5. In fact, in this case the doctor 12 is simply removed whileallowing the ink feed roller 3 to rotate in the clockwise direction.Thus, the ink reserve 5 is carried along by the peripheral surface ofthis ink feed roller 3 towards the additional doctor 13 which collectsthis ink and directs same towards the discharge through 14.

Although the attached drawings show two separate motors 11 and 19 fordriving on the one hand rollers 1 and 2, and on the other hand roller 3,it will readily occur to anybody conversant with the art that the inkfeed roller 3 may also be driven from the same motor 11 rotatablydriving the inking roller 2 by providing to this end a variable-speedgearing in the transmission system between the motor and the ink feedroller 3.

-In the foregoing reference is made primarily to the supply of ink tothe inking roller of an offset machine. However, it would not constitutea departure from the basic principles of this invention to apply thisinvention to the distribution of a regular, thin film of high-viscosityfluid on a cylinder or roller line with or consisting of relativelyflexible elastic material.

Furthermore, although the present invention has been described inconjunction with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit and scope of the invention, as those skilled in the art willreadily understand. Such modifications and variations are considered tobe within the purview and scope of the invention and appended claim.

What I claim is;

A device for distributing a thin regular film of a highviscosity liquidon the surface of a roller of flexible material, which is applicablenotably to the inking of a fattyink printing machine and comprises adistributor and wiper roller of relatively hard material tangent to saidroller of flexible material along a contact line, an ink fountainoverlying said contact line, means for rotatably supporting said rollerof flexible material and said distributor and wiper roller at theirends, means for rotatably driving said roller of flexible material andconveying a liquid film directly from said contact line, without usingany intermediate equalizer roller engaging said roller of flexiblematerial, means for rotatably driving said distributor and wiper rollerin the same direction as said roller of flexible.

material, a doctor disposed with its operative edge engaging theperipheral surface of said distributor and wiper roller above saidcontact line and in the vicinity of said ink fountain, said roller 0fflexible material and said distributor and wiper r-oller exerting oneach other a pressure adapted to form on the surf-ace of said roller offlexible material, throughout its length, a liquid film of constantthickness independently of the variation in the local contact pressurebetween said distributor and wiper roller and said roller of flexiblematerial along their contact line, and means for varying the velocity ofrotation of said distributor and wiper roller in relation to that ofsaid roller of flexible material in order to control the thickness ofthe liquid film coating said roller of flexible material.

References Cited by the Examiner UNITED STATES PATENTS 1,780,695 11/1930Alger l01350 1,873,235 8/1932 Wood 10135O 2,513,394 7/1950 Barrett et al1l8262 X 2,531,036 11/1950 Goettsch 118-262 X 2,674,299 4/ 1954 Bruker118262 X 2,830,555 4/1958 Barrett 1l8262 X 2,842,092 7/1958 Pomper118262 X 2,870,738 1/1959 Jacobs et al. 118262 X ROBERT E. PULFREY,Primary Examiner.

J. R. FISHER, Assistant Examiner.

